You might want to think about a mini-spare and jack kit, at least for road trips. Slime and a compressor can't fix every puncture.

If you have any DIY ability, having a spare can also allow you do to DIY tire rotations. Even with xDrive, your back tires will still likely wear faster than your front ones. Frau Putzer's rear tires wear 50% faster on her xDrive. My rear tires wear 100% faster on my sDrive. Rotating the tires will get you out of buying tires two at a time.

Here's even a bigger reason to rotate your tires. Since you have xDrive, keeping the average tread depth of the front tires and the average tread depth of the back tires the same (through rotation) will prevent the constant grinding and wear of the clutches in your xDrive transfer case.

I ditched my OE Goodyear LS2 RFT's at 31k miles, and put on Michelin PSS's. The difference in drive and handling were profound. Just driving over the one-inch high ridge of the street gutter at the exit of the dealer's driveway was so much smoother that I stopped and checked the tire pressures before my 95 mile drive home. I wish I'd ditched my RFT's at 31 miles instead of 31k miles.

 

Can someone explain the performance, comfort, speed and whatever other trade offs that people are experiencing with and without run-flats? Just bought a BMW after years of leasing Japanese and haven't had to deal with ties in like 20 years.

 

The underlying problem with RFT's is that the sidewalls can't stretch in the circumferential direction as much as with a non-RFT radial tire.

Radial tires are called that because the cords in the sidewalls are all in the radial direction, unlike with the old "bias-ply" or "diagonal-ply" tires which had the cords going in multiple directions. Radial cords allow the sidewalls to stretch in the circumferential direction. The rubber in between the cords can easily stretch. That allows the sidewalls to bulge (at the bottom of the tire where it's carrying the weight of the car). That sidewall bulging allows the tread of the tires to conform to the pavement. Without the sidewall bulging, the tread would "dimple" in the center of the contact patch with the pavement.

The best example of "dimpling" is that of a flat basketball or soccer ball. The flat spot is not flat, it's concave. That maintains the total surface area of the ball. That dimpling is why bias-ply tires wore out faster, had less adhesion, and had reduced fuel economy compared to radial tires. The rigid sidewalls of RFT's, even radial RFT's, prevents the sidewalls from stretching and deforming, and that brings back all the old problems of bias-ply tires. Additionally, the ride of RFT's is much harsher than similar non-RFT's. You can fix the uneven wear with over-inflation. But, then the ride and adhesion get even worse.

A big "gotcha" with RFT's is that after an RFT's is used without air pressure, the integrity of the sidewall is compromised and the tire is unsafe to use. An RFT will allow you to go up to 50 miles without air pressure. The catch is you'll need a new tire when you get there.

BMW's always used non-RFT's on M cars, and is now offering non-RFT's and spare tires as options on most of their non-M cars.

 

I won't do it again but I Slime plugged a RFT tire with 3 of the Slime strips and drove 3,000 miles on it for a trip. Replaced it when I got back. Not recommended. Just sharing my experience. I have a tire problem.

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I won't do it again but I Slime plugged a RFT tire with 3 of the Slime strips and drove 3,000 miles on it for a trip. Replaced it when I got back. Not recommended. Just sharing my experience. I have a tire problem. View attachment 854871

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I like saving a worn out tire that has almost perfectly even wear and is down to the wear bars. It's (further) evidence of my genius.

 

RFT's can literally be a life saver if you have a blowout in a place where it's not safe to change a tire. I used to drive the urban interstates of the northeast. I remember thinking "I'd hate to have a blowout here."

But, relatively few tire deflations are blowouts. Most are slow leaks, and modern TPMS's usually give you plenty of warning that there's a problem that needs your attention. I suspect that a lot of blowouts started out as a slow leak, where the lack of TPMS allowed the slow leak to turn into a blowout without warning.

I've driven about 1M miles in my life, and I've only had one blowout. It wasn't caused by a puncture, but by a rubber valve stem failure. TPMS's incorporate metal valve stems. So, the cause of my one blowout is now eliminated. We were discussing this last week at lunch. Two of my lunchmates, both in their mid to late 50's, said they'd had one and two blowouts in their lives. Between metal valve stems and TPMS, the chance of having a blowout is less than it used to be.

RFT's are a benefit to car manufacturers, because they don't have to include a spare tire. That saves money, weight, and volume. BMW often fills the volume where the spare would have gone with third row seats (X5), batteries for hybrid's, or large, low-back-pressure mufflers (M cars).

RFT's have some type of marking. Bridgestone calls them "RSC's." Michelin calls them "ZP's." There's also a "RUNFLAT" marking on the sidewalls. If your BMW has the original tires, and it doesn't have a spare tire, and it's not an M car, it's a good bet they're RFT's.

 

I have now had 8 RFT punctured tires in 3 1/2 years. I mostly blame it on being in a new construction neighborhood where I pick up errant screws and nails. Every one of the I drove for more than 100 miles until I had the time to have another one installed by a good tire shop. This would have never happens with a regular tire. It’s a tough decision to make but I am considering a switch to non run flats so I can take my car out in some snow.


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My mother lived in a massive apartment complex for ten years. It took them almost that long to complete it. It was owned by a guy who had his own construction company. When business was slow from customer projects, he'd add another section to his apartment complex. My mother was constantly getting flat tires. My routine was to go see her early Sunday mornings. I'd check and adjust her tire pressures before sunlight heated up the tires. If one tire was down a PSI or two, I went looking for and found an embedded nail or screw.

I live about ten miles west of the devastation area of Hurricane Michael. My town was mostly unscathed. But the towns to the east were trashed. Everybody over there was getting flat tires for months. I stopped going over there, and we still haven't been over there in our new X3. The county landfill in north of my town. The debris trucks came through my town on the way to the landfill, dropping crap on our roads.

U-stor-it complexes are a bad place to pick up nails and screws, too. I rent a garage in one. I purposely got one as close to the complex entrance as I could get.

 

Go to modernspare.com. The will fix you up with with a aftermarket spare that fits and that's capable of higher speed driving (not limited to 50 mph)

Remember to test fit your aftermarket spare on both the front and rear hubs. I have a 2023 760ix w/ M-Sport calipers and I needed a 5mm spacer and longer bolts for mounting on the rear hub. Front fit was OK.